Making the ChildConnectionAllocator start the connections.

The ChildConnectionAllocator now starts the connections it creates.
This allows us to:
- move the useStrongBinding parameter to the ChildConnectionAllocator
  constructor
- merge ChildProcessConnection.Deathcallback and
  ChildProcessConnection.StartCallback into one interface
  (ChildProcessConnection.ServiceCallback)

Bug: 702316
Change-Id: Idfe1b9a42487055c4d9171f50614093bd6e2c9d7
Reviewed-on: https://chromium-review.googlesource.com/546656
Reviewed-by: Bo Liu <boliu@chromium.org>
Commit-Queue: Jay Civelli <jcivelli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#482509}
12 files changed